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Message-ID: <87tv54syv8.fsf@cloudflare.com>
Date: Thu, 09 Jan 2020 11:33:31 +0100
From: Jakub Sitnicki <jakub@...udflare.com>
To: John Fastabend <john.fastabend@...il.com>
Cc: bpf@...r.kernel.org, netdev@...r.kernel.org, ast@...nel.org,
daniel@...earbox.net
Subject: Re: [bpf PATCH 3/9] bpf: sockmap/tls, push write_space updates through ulp updates
On Wed, Jan 08, 2020 at 10:14 PM CET, John Fastabend wrote:
> When sockmap sock with TLS enabled is removed we cleanup bpf/psock state
> and call tcp_update_ulp() to push updates to TLS ULP on top. However, we
> don't push the write_space callback up and instead simply overwrite the
> op with the psock stored previous op. This may or may not be correct so
> to ensure we don't overwrite the TLS write space hook pass this field to
> the ULP and have it fixup the ctx.
>
> This completes a previous fix that pushed the ops through to the ULP
> but at the time missed doing this for write_space, presumably because
> write_space TLS hook was added around the same time.
>
> Fixes: 95fa145479fbc ("bpf: sockmap/tls, close can race with map free")
> Signed-off-by: John Fastabend <john.fastabend@...il.com>
> ---
> include/linux/skmsg.h | 12 ++++++++----
> include/net/tcp.h | 6 ++++--
> net/ipv4/tcp_ulp.c | 6 ++++--
> net/tls/tls_main.c | 10 +++++++---
> 4 files changed, 23 insertions(+), 11 deletions(-)
>
> diff --git a/include/linux/skmsg.h b/include/linux/skmsg.h
> index b6afe01f8592..14d61bba0b79 100644
> --- a/include/linux/skmsg.h
> +++ b/include/linux/skmsg.h
> @@ -359,17 +359,21 @@ static inline void sk_psock_restore_proto(struct sock *sk,
> struct sk_psock *psock)
> {
> sk->sk_prot->unhash = psock->saved_unhash;
> - sk->sk_write_space = psock->saved_write_space;
>
> if (psock->sk_proto) {
> struct inet_connection_sock *icsk = inet_csk(sk);
> bool has_ulp = !!icsk->icsk_ulp_data;
>
> - if (has_ulp)
> - tcp_update_ulp(sk, psock->sk_proto);
> - else
> + if (has_ulp) {
> + tcp_update_ulp(sk, psock->sk_proto,
> + psock->saved_write_space);
> + } else {
> sk->sk_prot = psock->sk_proto;
> + sk->sk_write_space = psock->saved_write_space;
> + }
I'm wondering if we need the above fallback branch for no-ULP case?
tcp_update_ulp repeats the ULP check and has the same fallback. Perhaps
it can be reduced to:
if (psock->sk_proto) {
tcp_update_ulp(sk, psock->sk_proto, psock->saved_write_space);
psock->sk_proto = NULL;
} else {
sk->sk_write_space = psock->saved_write_space;
}
Then there's the question if it's okay to leave psock->sk_proto set and
potentially restore it more than once? Reading tls_update, the only user
ULP 'update' callback, it looks fine.
Can sk_psock_restore_proto be as simple as:
static inline void sk_psock_restore_proto(struct sock *sk,
struct sk_psock *psock)
{
tcp_update_ulp(sk, psock->sk_proto, psock->saved_write_space);
}
... or am I missing something?
Asking becuase I have a patch [0] like this in the queue and haven't
seen issues with it during testing.
-jkbs
[0] https://github.com/jsitnicki/linux/commit/2d2152593c8e6c5f38548796501a81a6ba20b6dc
> psock->sk_proto = NULL;
> + } else {
> + sk->sk_write_space = psock->saved_write_space;
> }
> }
>
> diff --git a/include/net/tcp.h b/include/net/tcp.h
> index e460ea7f767b..e6f48384dc71 100644
> --- a/include/net/tcp.h
> +++ b/include/net/tcp.h
> @@ -2147,7 +2147,8 @@ struct tcp_ulp_ops {
> /* initialize ulp */
> int (*init)(struct sock *sk);
> /* update ulp */
> - void (*update)(struct sock *sk, struct proto *p);
> + void (*update)(struct sock *sk, struct proto *p,
> + void (*write_space)(struct sock *sk));
> /* cleanup ulp */
> void (*release)(struct sock *sk);
> /* diagnostic */
> @@ -2162,7 +2163,8 @@ void tcp_unregister_ulp(struct tcp_ulp_ops *type);
> int tcp_set_ulp(struct sock *sk, const char *name);
> void tcp_get_available_ulp(char *buf, size_t len);
> void tcp_cleanup_ulp(struct sock *sk);
> -void tcp_update_ulp(struct sock *sk, struct proto *p);
> +void tcp_update_ulp(struct sock *sk, struct proto *p,
> + void (*write_space)(struct sock *sk));
>
> #define MODULE_ALIAS_TCP_ULP(name) \
> __MODULE_INFO(alias, alias_userspace, name); \
> diff --git a/net/ipv4/tcp_ulp.c b/net/ipv4/tcp_ulp.c
> index 12ab5db2b71c..38d3ad141161 100644
> --- a/net/ipv4/tcp_ulp.c
> +++ b/net/ipv4/tcp_ulp.c
> @@ -99,17 +99,19 @@ void tcp_get_available_ulp(char *buf, size_t maxlen)
> rcu_read_unlock();
> }
>
> -void tcp_update_ulp(struct sock *sk, struct proto *proto)
> +void tcp_update_ulp(struct sock *sk, struct proto *proto,
> + void (*write_space)(struct sock *sk))
> {
> struct inet_connection_sock *icsk = inet_csk(sk);
>
> if (!icsk->icsk_ulp_ops) {
> + sk->sk_write_space = write_space;
> sk->sk_prot = proto;
> return;
> }
>
> if (icsk->icsk_ulp_ops->update)
> - icsk->icsk_ulp_ops->update(sk, proto);
> + icsk->icsk_ulp_ops->update(sk, proto, write_space);
> }
>
> void tcp_cleanup_ulp(struct sock *sk)
> diff --git a/net/tls/tls_main.c b/net/tls/tls_main.c
> index dac24c7aa7d4..94774c0e5ff3 100644
> --- a/net/tls/tls_main.c
> +++ b/net/tls/tls_main.c
> @@ -732,15 +732,19 @@ static int tls_init(struct sock *sk)
> return rc;
> }
>
> -static void tls_update(struct sock *sk, struct proto *p)
> +static void tls_update(struct sock *sk, struct proto *p,
> + void (*write_space)(struct sock *sk))
> {
> struct tls_context *ctx;
>
> ctx = tls_get_ctx(sk);
> - if (likely(ctx))
> + if (likely(ctx)) {
> + ctx->sk_write_space = write_space;
> ctx->sk_proto = p;
> - else
> + } else {
> sk->sk_prot = p;
> + sk->sk_write_space = write_space;
> + }
> }
>
> static int tls_get_info(const struct sock *sk, struct sk_buff *skb)
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